Minor doc fix.
Minor doc fix.

yaojingwu1992/XlsxWriter,jmcnamara/XlsxWriter,mdeemer/XlsxWriter,liukaijv/XlsxWriter,Thhhza/XlsxWriter,yaojingwu1992/XlsxWriter,applicationdevm/XlsxWriter,applicationdevm/XlsxWriter,gechong/XlsxWriter,yaojingwu1992/XlsxWriter,gechong/XlsxWriter,seize-the-dave/XlsxWriter,jkyeung/XlsxWriter,Thhhza/XlsxWriter,jkyeung/XlsxWriter,jmcnamara/XlsxWriter,jvrsantacruz/XlsxWriter,jvrsantacruz/XlsxWriter,gechong/XlsxWriter,seize-the-dave/XlsxWriter,liukaijv/XlsxWriter,applicationdevm/XlsxWriter,mdeemer/XlsxWriter,liukaijv/XlsxWriter,jkyeung/XlsxWriter,jvrsantacruz/XlsxWriter,mdeemer/XlsxWriter,mdeemer/XlsxWriter,jkyeung/XlsxWriter,Thhhza/XlsxWriter,seize-the-dave/XlsxWriter,jmcnamara/XlsxWriter,jmcnamara/XlsxWriter,yaojingwu1992/XlsxWriter,seize-the-dave/XlsxWriter,applicationdevm/XlsxWriter,Thhhza/XlsxWriter,gechong/XlsxWriter,jvrsantacruz/XlsxWriter,liukaijv/XlsxWriter